The studies proposed for the current year are: 1) to continue the longitudinal studies in children of the mechanical properties of the lung (elastic recoil pressures, lung volumes, maximum expiratory flow-volume curves) 2) to evaluate lung mechanics including frequency dependence of compliance and gas exchange in patients who had congenital lobar emphysema in early childhood, 3) to relate anatomic dead space, elastic recoil of the lung and maximum expiratory flow in children and young adults, (4 to extend our method of obtaining air expiration to a low lung volume close to residual volume to obtain measurements of "closing volume" in infants and 5) to apply our techniques of obtaining maximal expiratory flow volume curves using gases of different density to infants with chronic pulmonary disease.